Removal of Typical Volatile Organic Compounds in Condensed Freshwater by Activated Persulfate during Interfacial Solar Distillation

Abstract

Recently, seawater desalination based on interfacial solar heating has attracted attention because of its environmental protection and high photothermal conversion efficiency. However, the high air–water interface temperature may cause freshwater quality safety risks because the volatile organic compounds (VOCs) in seawater are more likely to evaporate and condense into freshwater. In this work, typical VOCs (phenol) were prevented from entering into the condensed freshwater by using activated persulfate to take full advantage of interfacial solar distillation. The results showed that the addition of both peroxodisulfate (PDS) and peroxymonosulfate (PMS) could effectively reduce the concentration of phenol in condensed freshwater. The phenol’s distillation concentration rate (RD) was reduced from 74.4% to 14.3% with PMS and 20.5% with PDS. The Cl– was the main factor for activation of PMS, while carbon black, light, and heat were the main factors for activation of PDS. Meanwhile, PMS is better suited for removing VOCs due to its lower oxidant dosage and chlorinated disinfection byproducts compared with PDS. Finally, when real seawater samples were used as the source water for solar distillation, the water quality of typical indicators was lower than the limits set by Drinking Water Quality in China, US EPA, and WHO.